Recently, reversible thermal sensitive recording media (rewritable cards/rewritable sheets) has increased in popularity. This process consists of a base, e.g., paper, nonwoven fabric, cloth, vinyl chloride, synthetic resins such as polyethylene terephthalate, film/sheet/card-form of metal and glass, and a recording part consisting of a thermal reversible recording layer which colors and de-colors repeatedly by heating.
Typically, a glass glaze layer is placed on a first side of a head substrate board, a strip-shaped heating resistive element is formed on the glass glaze layer and a pair of electrodes is placed on both ends of the strip-shaped heating resistive element. The electrodes are powered by wires on the wiring board, inserted through the backside of the head substrate board. The heating resistive element heats by voltage applied by the electrodes at both ends of the strip-shaped heating resistive element and the temperature of the strip-shaped heating resistive element is controlled by the amount of current. The head substrate board is attached to the aluminum base using an adhesive. A cavity on the base of the head substrate board is disposed under the strip-shaped heating resistive element to control heat escaping from the head substrate board to the aluminum base. Erasing occurs by the recording media being engaged by a roller and passing through in contact with the heating resistive element.
For toner fusing, heating from top and bottom is required. A heating roller fusing apparatus uses the heating rollers having a heater lamp, e.g., a halogen bulb, inside as fuser rollers. A heating belt fusing apparatus has a fusing roller which is connected to a heating roller with a belt; heating is done by pressing the media against the heated belt by the heating roller rotated to the fusing roller side and the pressing roller which has the heater internally.
There are multiple problems in the art. One is glass abrasion damage or unstable resistance value of the heating resistive element since the rubber roller and the heating resistive element are pressed together.
Another problem is that there are electrodes on both ends of the heating resistive element. However, it is not possible to connect the electrode surface and the wiring board directly as the media passes through the surface of the heating resistive element. This creates a complex manufacturing process since a connection has to be made on the backside of the substrate by making the connecting layer and connecting to the wiring board.
Another problem is the difficulty to maintain stable heating since the temperature drops if the media comes in continuously; this is due to the heat capacity of the heating resistive element being small when it is heated directly.
Another challenge for maintaining stable heating is that the temperature increases when there is no media coming in for a long period.
Another problem is that the power consumption increase and waste becomes an issue when the heater lamp is inserted into the heating roller to raise the whole body temperature for those cases of heating roller toner fusing apparatus or heating belt toner fusing apparatus.
An additional problem is the long duration for the heating roller surface to reach the predetermined temperature as well as keeping the heating roller surface temperature constant.
For toner fusing, heating from top and bottom is necessary. A heating roller fusing apparatus utilizes heating rollers which use a heater lamp, e.g., a halogen bulb, inside the heating roller to form a fuser roller. A heating belt fusing apparatus has a fusing roller connected to the heating roller with a belt. Heating is accomplished by pressing the media against the heated belt as the heating roller is rotated to the fusing roller side and by the pressing roller which has the heater internally.
Attempts to address problems in the art have been directed to configurations where the media does not engage the side where the heating resistive element is installed on the head substrate board, but instead engages on the opposite side of the side where the heating resistive element is, or, alternatively, on the lateral face of the heating resistive element.
However, when such a structure is employed it is not possible to make the surface completely smooth even if it is over-coated with a low friction coefficient and hard material such as diamond-like carbon on alumina, which the head substrate board is usually made of, which is very hard and lacks smoothness even if large protruding objects are pre-removed from the surface, unless the surface goes through lapping or polishing processes. Therefore media surfaces such as plastic or cardboard with wax-processed surface are easily damaged. On the other hand, there is increased cost issue if the head substrate surface processes were incorporated into the production steps.
One solution is a configuration where the heating head does not touch the media on the heating resistive element on the substrate board; the contact side is the backside of the heating resistive element side or lateral side which is adjacent to the side where the heating resistive element is on. Alumina which is usually used for the substrate board is hard and the surface is not smooth even if large protruding objects are pre-removed from the surface.
However, it is difficult to make this surface completely smooth even if the surface is polished or lapped with a layer of low coefficient of friction and hard material such as the diamond like carbon is formed. If this type of structure is used, the media, which is made of plastic or cardboard with wax-process, can be easily damaged. Also, there is an increased cost since the surface smoothing process is incorporated in the production steps.